Glottographic Measures Before and After Levodopa Treatment in Parkinson's Disease

Abstract

Objectives: Investigate the usefulness of acoustic and glottographic measures for detecting effects of levodopa (L‐dopa) treatment on vocal function of individuals with idiopathic Parkinson's disease. Study Design: Compare recordings of vowels sustained at a target comfortable loudness level obtained before and after L‐dopa treatment from 15 individuals with idiopathic Parkinson's disease showing signs of tremor. Methods: A simultaneous acoustic, airflow, and electroglottographic recording technique was employed to record vowels phonated by subjects before and after L‐dopa treatment. Algorithms were developed to derive from the recorded signal measures of fundamental frequency, SPL, airflow rate, speed quotient (ratio of glottal opening to closing time time), and short‐ and long‐term phonatory instability. A series of paired Student t tests or signed rank tests were performed to compare the pretreatment and posttreatment groups on these measures. Results: Measures of speed quotient, acoustic shimmer (cycle‐to‐cycle amplitude perturbation), and the extent of tremor derived from acoustic intensity contours were found to significantly decrease after medication. Sound pressure level tended to increase after medication. The acoustic jitter (cycle‐to‐cycle frequency perturbation) and the extent of tremor derived from airflow signals did not significantly differentiate between premedication and postmedication voices. Conclusions: Objective measures of acoustic and electroglottographic signals are useful in monitoring the pharmacologic response of Parkinson's disease, reflecting decrease of laryngeal rigidity and short‐ and long‐term acoustic amplitude fluctuation after L‐dopa treatment.